public class Circle {

    double radius;
    double area;


    /**
     * 构造函数，用于创建指定半径的圆
     * @param radius 圆的半径
     */
    public Circle(double radius){
        this.radius = radius;
        this.area = Math.PI * radius * radius;
    }

    Circle(){
    }

    void printArea(double radius){
        System.out.println("The area of circle is:" + Math.PI * radius * radius);
    }
    double showRadius(double area){
        double radius = Math.sqrt(area/Math.PI);
        return radius;
    }
}
